Environment

Polar researchers have surveyed remote areas of the Antarctic seas by recruiting elephant seals to collect data for them.

Mounting evidence that the Southern Ocean is warming more rapidly than expected has fuelled interest in temperature dynamics and sea-ice formation rates near the South Pole. But thick sea ice cover makes it virtually impossible to collect data by conventional methods such as buoyant floats and research ships.

Now a team led by Jean-Benoit Charrassin of France's National Museum of Natural History in Paris have got round the problem - by gluing electronic sensors to the heads of 58 wild elephant seals.

The sensor can take accurate measurements of salinity, temperature and depth, and relay them by satellite. It resembles a toy tank and is attached to the seal's skin using epoxy, an extremely strong, waterproof glue.

Scientific seals

Elephant seals breed on Antarctic islands, but forage for food in the inaccessible regions of the Southern Ocean. The seals gather information about the temperature and salinity of the water under the sea ice each time they dive for food. When they surface, the data is transmitted to the researchers via satellite.

"The seals are in a key area and they can measure important parameters that are difficult to obtain otherwise," Charrassin.

The idea of using marine animals to patrol the oceans isn't new, but this is the first time it has been done on such a large scale.

The devices remain attached to the seals for up to a year, until they moult. This means that repeated measurements of the same area can be taken over a long time period, and the researchers need only come to Antarctica once a year to attach new sensors.

Watching the seas

"I consider it a real breakthrough in ocean observation," says Michael Fedak, part of the team who designed and built the data transmitters.

According to Susan Gallon, of the Sea Mammal Research Unit, University of St Andrews, UK, this approach has enabled the collection of novel oceanographic data that has never before been possible, and will provide valuable information for monitoring the response of this region to climate change.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0800790105

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